Electronic component package, printed circuit board, and method of inspecting the printed circuit board

ABSTRACT

There is provided a ball grid array (BGA) electronic component package having a configuration which is capable of improving mounting efficiency as well as preventing footprints from breaking away at circuit-connecting portions of the electronic component package. The BGA package has reinforcing bumps formed in an area located outward of a predetermined area in which conventional circuit-connecting bumps are arranged. Therefore, even if a shock is applied to the BGA package e.g. when a printed circuit board having the BGA package mounted thereon is carelessly dropped during the manufacturing work, at the outer or peripheral portion of the BGA package, which is most sensitive to such a shock, the shock is absorbed by the reinforcing bumps and reinforcing footprints which have no electrical connection with the circuitry of the electronic component package. Thus, the footprints formed on a mounting portion of the BGA package and those formed on the printed circuit board can be prevented from breaking away or being cracked.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a surface-mount package, aprinted circuit board having the package mounted thereon, and a methodof inspecting the assembled printed circuit board and package, and moreparticularly, to a ball grid array package, a printed circuit boardhaving the ball grid array package mounted thereon, and a method ofinspecting the assembled printed circuit board and ball grid arraypackage.

[0003] 2. Description of the Related Art

[0004] In recent years, a ball grid array (hereinafter referred to as“BGA”) package, which is a key device in high-density mountingtechnology, has been applied to communications devices such as aportable telephone. Moreover, the BGA package is now starting to beapplied to trunk communications devices. It is expected that the BGApackage continues to be applied to a wider range of applications as anLSI (Large-Scale Integration) package, to replace the large-sized QFP(Quad Flat Package) with a fine lead pitch.

[0005] FIGS. 18(A) and 18(B) schematically show external configurationsof a conventional BGA package. FIG. 18(A) is a side view, while FIG.18(B) is a bottom view. The BGA package 200 has a package body 201 inwhich semiconductor chips are laminated, and the package body 201 has abottom thereof formed with a plurality of footprints (pads) 202 on whichrespective ball-shaped solder bumps 203 are formed on the respectivefootprints 202.

[0006] The BGA package 200 is mounted on a printed circuit board bysoldering the solder bumps 203 onto the printed circuit board.

[0007]FIG. 19 shows the BGA package 200 mounted on the printed circuitboard. The printed circuit board 204 is formed with footprints 205thereon to which the respective solder bumps 203 are soldered. In orderto solder the BGA package 200 onto the printed circuit board 204,similarly to an operation for soldering typical surface-mountcomponents, solder paste 206 is applied onto the respective footprints205 by a screen printing process, and then the BGA package 200 is placedon the solder paste 206, followed by melting the solder paste 206 andthe solder bumps 203 by the use of a heating apparatus.

[0008] In general, if the printed circuit board 204 having the BGApackage 200 mounted thereon receives a shock e.g. when it is carelesslydropped while being handled, the printed circuit board 204 is distorted,which affects solder joints on the BGA package 200. Each terminal of theBGA package 200 has a larger solder joint area than that of conventionalcomponents having leads connected thereto, so that soldered jointstrength between the solder bumps 203 and the footprints 205 isrelatively high. This prevents the solder bumps 203 and the footprints205 from breaking away from each other.

[0009] However, if joint strength between the package body 201 of theBGA package 200 and the respective footprints 202 or between a substratesurface of the printed circuit board 204 and the respective footprints205 is low, forces generated by any distortion of the printed circuitboard 204 are likely to crack some of the footprints 202, 205 or causethe same to break away from the package body 201 or the printed circuitboard 204. It is known that when the printed circuit board 204 receivesa shock, the solder bumps 203 in the outermost rows and columns areespecially prone to such cracking and breakaway since vibrations,warping, expansion, and/or contraction, have the maximum effect at theedge or peripheral portions of the printed circuit board 204.

[0010] To overcome this problem, a method is conventionally employed inwhich a reinforcing adhesive 207 is applied to the outermost solderbumps 203 and its vicinity, as shown in FIG. 19, so as to securely jointhe outermost solder bumps 203, the package body 201, and the printedcircuit board 204 to each other.

[0011] However, this method increases the number of manufacturing steps,resulting in degraded working efficiency. Moreover, when the BGA package200 is defective, it is required to discard the printed circuit board204 together with the package 200 rather than simply replace the package200 with a new one. This results in the waste of materials as well as anincrease in manufacturing costs.

[0012] Further, since it is impossible to judge by visual inspectionwhether any of the solder joints on the BGA package 200 is defective,the inspection of electrical connections of the solder joints isconventionally performed at an electronic testing stage of themanufacturing process. However, the conventional electronic test cannotdetect either a breakaway or a crack of the footprint 202 or 205 unlessthere is a disconnection in any pattern connected to the solder bumps203.

SUMMARY OF THE INVENTION

[0013] A first object of the present invention is to provide anelectronic component package and a printed circuit board which arecapable of improving working efficiency in mounting the electroniccomponent package on the printed circuit board, and at the same timepreventing a breakaway of footprints formed on the electronic componentpackage for circuit connection.

[0014] A second object of the invention is to provide a method ofinspecting the printed circuit board, which is capable of detecting adefect, such as a breakaway and a crack, of footprints.

[0015] To accomplish the first object, according to a first aspect ofthe invention, there is provided an electronic component package of ballgrid array type. The electronic component package is characterized bycomprising a plurality of circuit-connecting bumps formed in apredetermined area, and at least one reinforcing bump formed in an arealocated outward of the predetermined area, in a manner such that the atleast one reinforcing bump is connectable to at least one reinforcingpattern formed on a printed circuit board.

[0016] To accomplish the second object, according to a second aspect ofthe invention, there is provided a method of inspecting a printedcircuit board having an electronic component package mounted thereon.This method is characterized by comprising the steps of forming a bridgecircuit between reinforcing bumps formed on the electronic componentpackage, and reinforcing footprints formed on the printed circuit boardin a manner such that the reinforcing bumps are connected to thereinforcing footprints, and detecting a change in a resistance value ofthe bridge circuit to thereby detect a defect of the printed circuitboard.

[0017] The above and other objects, features and advantages of thepresent invention will become apparent from the following descriptionwhen taken in conjunction with the accompanying drawings whichillustrate preferred embodiments of the present invention by way ofexample.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a partial sectional view of a printed circuit board, anda BGA package mounted thereon, according to a first embodiment of thepresent invention;

[0019] FIGS. 2(A) and 2(B) are views showing the external configurationof the BGA package according to the first embodiment, in which:

[0020]FIG. 2(A) is a bottom view showing part of the BGA package; and

[0021]FIG. 2(B) is a sectional view taken on line X-X of FIG. 2(A);

[0022] FIGS. 3(A) and 3(B) are views showing the general configurationof the printed circuit board on which the BGA package according to thefirst embodiment is mounted, in which:

[0023]FIG. 3(A) is a plan view schematically showing the externalconfiguration of the printed circuit board; and

[0024]FIG. 3(B) is an enlarged view showing part of a BGA package area;

[0025]FIG. 4 is a bottom view showing the external configuration of aBGA package according to a second embodiment of the invention;

[0026] FIGS. 5(A) and 5(B) are views showing the sectional configurationof the BGA package according to the second embodiment, in which:

[0027]FIG. 5(A) is a sectional view taken on line X1-X1 of FIG. 4; and

[0028]FIG. 5(B) is a sectional view taken on line X2-X2 of FIG. 4;

[0029] FIGS. 6(A) and 6(B) are views showing a BGA package according toa third embodiment of the invention, in which:

[0030]FIG. 6(A) is a bottom view showing part of the configuration ofthe BGA package; and

[0031]FIG. 6(B) is a sectional view taken on line X3-X3 of FIG. 6(A);

[0032] FIGS. 7(A) and 7(B) are views showing the sectional configurationof a BGA package according to a fourth embodiment of the invention, inwhich:

[0033]FIG. 7(A) is a bottom view showing part of the BGA package; and

[0034]FIG. 7(B) is a sectional view taken on line X4-X4 of FIG. 7(A);

[0035]FIG. 8 is a plan view showing the configuration of a printedcircuit board according to a fifth embodiment of the invention;

[0036]FIG. 9 is a plan view showing the configuration of a printedcircuit board according to a sixth embodiment of the invention;

[0037]FIG. 10 is a view showing a variation of the printed circuit boardaccording to the sixth embodiment;

[0038] FIGS. 11(A) and 11(B) are views showing the configuration of aprinted circuit board according to a seventh embodiment of theinvention, in which:

[0039]FIG. 11(A) is a plan view showing part of the printed circuitboard; and

[0040]FIG. 11(B) is a sectional view taken on line X5-X5 of FIG. 11(A);

[0041] FIGS. 12(A) and 12(B) are views showing the configuration of aprinted circuit board according to an eighth embodiment of theinvention, in which:

[0042]FIG. 12(A) is a plan view showing part of the printed circuitboard; and

[0043]FIG. 12(B) is a side view showing a fixing member in a mountedstate;

[0044] FIGS. 13(A) and 13(B) are views showing a mounting component foruse in mounting the fixing member for the printed circuit boardaccording to the eighth embodiment, in which:

[0045]FIG. 13(A) is a view schematically showing the generalconstruction of the mounting component; and

[0046]FIG. 13(B) is an enlarged view showing part of the mountingcomponent;

[0047] FIGS. 14(A) and 14(B) are views showing the configuration of aprinted circuit board according to a ninth embodiment of the invention,in which:

[0048]FIG. 14(A) is a plan view showing part of the printed circuitboard; and

[0049]FIG. 14(B) is a side view showing a fixing member in a mountedstate;

[0050]FIG. 15 is a bottom view showing a mounting surface of a BGApackage according to a tenth embodiment of the invention;

[0051]FIG. 16 is a plan view showing the configuration of a printedcircuit board according to the tenth embodiment;

[0052] FIGS. 17(A) and 17(B) are views showing the configuration of aprinted circuit board according to an eleventh embodiment of theinvention, in which:

[0053]FIG. 17(A) is a plan view showing part of the printed circuitboard; and

[0054]FIG. 17(B) is a sectional view taken on line X6-X6 of FIG. 17(A);

[0055] FIGS. 18(A) and 18(B) are views showing the externalconfiguration of a conventional BGA package, in which:

[0056]FIG. 18(A) is a side view showing the BGA package; and

[0057]FIG. 18(B) is a bottom view showing part of the BGA package; and

[0058]FIG. 19 is a view showing the conventional BGA package mounted ona conventional printed circuit board.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0059] Preferred embodiments of the present invention will be describedbelow with reference to accompanying drawings.

[0060] Referring first to FIGS. 1 to 3, description is made of a BGApackage according to a first embodiment of the invention. FIGS. 2(A) and2(B) show the external configuration of the BGA package. FIG. 2(A) is apartial bottom view of the BGA package, while FIG. 2(B) is a sectionalview taken on line X-X of FIG. 2(A). The BGA package 10 has a packagebody 11 defining therein a semiconductor building block 11 b in whichsemiconductor chips are laminated. As shown in FIG. 2(B), the packagebody 11 has a bottom 11 a formed with a plurality of footprints (pads)12 on which respective solder bumps are formed for connecting betweenterminals of the semiconductor building block 11 b and the circuitry ofa printed circuit board. Each of the solder bumps formed of solder isball-shaped.

[0061] Further, a plurality of reinforcing solder bumps 15 are formed onrespective footprints 14 in an area (shown by dotted lines in FIG. 2(A))11 c enclosing a solder bump area in which the solder bumps 13 arearranged. The reinforcing solder bumps 15 have no electrical connectionwith the circuitry of the BGA package 10. The bottom 11 a of the packagebody 11 has a resist 16 formed thereon. The resist 16 is printed ontothe bottom 11 a in a state in which the solder bumps 13 and thereinforcing solder bumps 15 are masked.

[0062] The BGA package 10 described above is mounted on the printedcircuit board by soldering the respective solder bumps 13 onto theprinted circuit board.

[0063] FIGS. 3(A) and 3(B) schematically show the general configurationof the printed circuit board on which the BGA package 10 according tothe first embodiment is mounted. FIG. 3(A) is a plan view of the printedcircuit board, while FIG. 3(B) shows part of a BGA package area of theprinted circuit board on an enlarged scale. As shown in FIG. 3(A), theprinted circuit board 20 has a component mounting surface 21 thatincludes the BGA package area 21 a onto which the BGA package 10 issoldered.

[0064] In the BGA package area 21 a, as shown in FIG. 3(B), there areformed a plurality of footprints (pads) 22 in a manner opposed to therespective solder bumps of the BGA package 10. Each of the solder bumps13 is soldered to a corresponding one of the footprints 22. Further, theBGA package area 21 a has an area 21 b enclosing an area in which thefootprints 22 are arranged, and in the area 21 b, there are formed aplurality of reinforcing footprints 23 in a manner opposed to therespective reinforcing solder bumps 15. Each of the reinforcing solderbumps 15 is soldered to a corresponding one of the reinforcingfootprints 23.

[0065]FIG. 1 is a sectional view showing part of the printed circuitboard 20 with the BGA package 10 mounted thereon. In order to solder theBGA package 10 onto the printed circuit board 20, solder paste isapplied by a screen printing method onto the footprints 22, 23 and thenthe BGA package 10 is placed on the printed circuit board such that eachof the circuit-connecting solder bumps 13 is placed on a correspondingone of the footprints 22 and each of the reinforcing solder bumps 15 isplaced on a corresponding one of the footprint 23.

[0066] Then, the printed circuit board 20 having the BGA package 10 andother circuit components, not shown in FIG. 1, mounted thereon is placedin a heating apparatus, and then the solder paste applied onto thefootprints 22, 23 is melted, whereby the solder bumps 13 and thereinforcing solder bumps 15 are soldered to the footprints 22, 23,respectively, by solders 24, 25. Thus, the mounting of the BGA package10 on the printed circuit board 20 is completed.

[0067] According to the above embodiment, the BGA package 10 mounted onthe printed circuit board 20 has the reinforcing solder bumps 15 formedin the area 21 b outward of the area in which are arranged theconventional solder bumps 13 for circuit connection, so that even if ashock is applied to the BGA package 10 e.g. when the printed circuitboard 20 is carelessly dropped during the manufacturing work, at theouter or peripheral portion of the BGA package, which is most sensitiveto such a shock, the shock is absorbed by the reinforcing solder bumps15 and footprints 23 which have no electrical connection with thecircuitry of the package 10, whereby it is possible to prevent thefootprints 12 formed on the mounting-area of the BGA package 10 and thefootprints 22 formed on the printed circuit board 20 from breaking awayor being cracked.

[0068] Further, since extra materials such as an adhesive can bedispensed with, the number of manufacturing steps can be reduced, and atthe same time, it is not required to discard the printed circuit board20 together with the BGA package 10 even if the BGA package 10 isdefective. Therefore, it is possible to enhance the working efficiencyand prevent waste of materials and an increase in manufacturing costs.

[0069] Although the figures illustrate the solder bumps 13 and thereinforcing solder bumps 15 on enlarged scale for purposes of clarity ofunderstanding, actually the solder bumps 13, 15 are smaller incomparison with the size of the BGA package 10, and the number thereofis larger than shown in the figures.

[0070] Next, a second embodiment of the present invention will bedescribed with reference to FIG. 4 and FIGS. 5(A) and 5(B).

[0071]FIG. 4 is a bottom view showing the external configuration of aBGA package according to the second embodiment. FIG. 5(A) is a sectionalview taken on line X1-X1 of FIG. 4, while FIG. 5(B) is a sectional viewtaken on line X2-X2 of the same. In FIGS. 5(A) and 5(B), illustration ofthe cross section of a package body 31 of the BGA package 30 is omitted.The package body 31 has a bottom 31 a formed with a plurality offootprints 32 (see FIG. 5(A)) on which respective ball-shaped solderbumps 33 are formed for circuit connection.

[0072] In an area 31 b (see FIG. 4) enclosing a solder bump area inwhich the solder bumps 33 are arranged, there are formed reinforcingsolder bumps 35 on a reinforcing pattern 34. The reinforcing pattern 34is formed such that all the reinforcing solder bumps 35 are connectablethereto. The reinforcing solder bumps 35 and the pattern 34 have noelectrical connection with the circuitry of the BGA package 30. Further,the bottom 31 a of the package body 31 is covered with a resist 36. Theresist 36 is printed in a state in which the solder bumps 33 and thereinforcing solder bumps 35 are masked.

[0073] According to the present embodiment, since the reinforcingpattern 34 is formed in a manner connectable to all the reinforcingsolder bumps 35, joint strength between the pattern 34 and the packagebody 31 is increased, which makes the printed circuit board with the BGApackage 30 mounted thereon more resistant to a shock.

[0074] The printed circuit board has a mounting surface configured to besubstantially identical to a state of the corresponding part of the BGApackage 30 from which the solder bumps 33 and the reinforcing solderbumps 35 are removed. More specifically, the mounting surface of theprinted circuit board is formed with one-piece pattern onto which thereinforcing solder bumps 35 are soldered. This provides the same effectsas obtained by the corresponding part of the BGA package 30.

[0075] Next, a third embodiment of the invention will be described withreference to FIGS. 6(A) and 6(B).

[0076] FIGS. 6(A) and 6(B) show the external configuration of a BGApackage according to the third embodiment. FIG. 6(A) is a bottom viewshowing part of the BGA package, while FIG. 6(B) is a sectional viewtaken on line X3-X3 of FIG. 6(A). In the figures, illustration of thecross section of a package body 41 of the BGA package 40 is omitted. Thepackage body 41 has a bottom 41 a formed with a plurality of footprints,not shown in the figures, on which respective ball-shaped solder bumps43 are formed for circuit connection.

[0077] In an area enclosing a solder bump area in which the solder bumps43 are arranged, reinforcing solder bumps 45 are formed on a reinforcingpattern 44 (see FIG. 6(B)). Out of the reinforcing solder bumps 45, aplurality of reinforcing solder bumps 451 (three reinforcing solderbumps in FIG. 6(B)) are formed on a pattern 441 in a corner of the area.The pattern 441 is formed such that all the reinforcing solder bumps 451in the corner are connectable thereto. The reinforcing solder bumps 45,451 and the patterns 44, 441 have no electrical connection with thecircuitry of the BGA package 40. Further, the bottom 41 a of the packagebody 41 is covered with a resist 46. The resist 46 is printed in a statein which the solder bumps 43 and the reinforcing solder bumps 45, 451are masked.

[0078] According to the present embodiment, even if the BGA package 40receives a shock e.g. when a printed circuit board having the samemounted thereon is carelessly dropped, most of the shock is absorbed bythe reinforced corners. That is, by forming a one-piece pattern 441 forthe reinforcing solder bumps 451 in each corner of the BGA package, itis possible to make the strength of the BGA package higher than whenfootprints are formed separately for the respective reinforcing solderbumps 451. This makes it possible to more positively prevent the solderbumps from breaking away. Although FIGS. 6(A) and 6(B) show theconfiguration of only one corner of the package body 41, it goes withoutsaying that the other three corners can have the same configuration.

[0079] On the other hand, the printed circuit board has a mountingsurface configured to be substantially identical to a state of thecorresponding part of the BGA package 40 from which the solder bumps 43and the reinforcing solder bumps 45, 451 are removed. More specifically,the mounting surface of the printed circuit board is formed with aone-piece pattern onto which the reinforcing solder bumps 451 aresoldered. This provides the same effects as obtained by thecorresponding part of the BGA package 40.

[0080] Next, a fourth embodiment of the present invention will bedescribed with reference to FIGS. 7(A) and 7(B).

[0081] FIGS. 7(A) and 7(B) show the external configuration of a BGApackage according to the fourth embodiment. FIG. 7(A) is a partialbottom view of the BGA package, while FIG. 7(B) is a sectional viewtaken on line X4-X4 of FIG. 7(A). In FIGS. 7(A) and 7(B), illustrationof the cross section of a package body 51 of the BGA package 50 isomitted. The package body 51 has a bottom 51 a formed with a pluralityof footprints 52 (see FIG. 6(B)) on which respective ball-shaped solderbumps 53 are formed for circuit connection.

[0082] Further, the package body 51 has corners each formed with aprotruding portion 51 b having a predetermined area. The protrudingportion 51 b is formed with a reinforcing pattern 54, and a plurality ofreinforcing solder bumps 55 (e.g. five reinforcing solder bumps 55) areformed on the pattern 54. The reinforcing pattern 54 is formed in onepiece such that all the reinforcing solder bumps 55 are connectablethereto. The reinforcing solder bumps 55 and the pattern 54 have noelectrical connection with the circuitry of the BGA package 50. Further,the bottom 51 a (including the protruding portion 51 b) of the packagebody 51 is covered with a resist 56. The resist 56 is printed in a statein which the solder bumps 53 and the reinforcing solder bumps 55 aremasked.

[0083] According to the present embodiment constructed above, even ifthe BGA package 50 mounted thereon receives a shock e.g. when a printedcircuit board having the same mounted thereon is carelessly dropped,most of the shock is absorbed by the protruding portions. This makes itpossible to prevent the solder bumps 53 for circuit connection frombreaking away from the footprints 52 and other similar inconveniences.Although FIGS. 7(A) and 7(B) show the configuration of only one cornerof the package body 51, it goes without saying that the other threecorners can have the same configuration.

[0084] On the other hand, the printed circuit board has a mountingsurface configured such that a pattern to which the reinforcing bumps 55are soldered is formed on an area corresponding to the protrudingportion 51 of the BGA package 50. This provides the same effects asobtained by the corresponding part of the BGA package 50. In thisconnection, it is preferred that the pattern to which the reinforcingbumps are soldered is substantially symmetrical with the pattern 54.

[0085] Next, a fifth embodiment of the present invention will bedescribed with reference to FIG. 8.

[0086]FIG. 8 is a plan view showing the configuration of a printedcircuit board according to the fifth embodiment. The printed circuitboard 60 has slots 62, 63, 64, 65 formed in the vicinity of respectivecorners of an area in which a BGA package 61 is mounted. Each of theslots 62, 63, 64, 65 has a width determined according to the thicknessof the printed circuit board 60. For instance, when the printed circuitboard 60 has a thickness of 1.6 mm, it is preferred that the slots 62,63, 64, 65 are each formed to have a width of approximately 2 mm. Whenthe printed circuit board 60 has a thickness of 0.8 mm, it is preferredthat the slots 62, 63, 64, 65 are each formed to have a width ofapproximately 1 mm.

[0087] According to this embodiment, since the printed circuit board 60is formed with the slots 62, 63, 64, 65, even if the printed circuitboard 60 is dropped, a shock due to the drop is absorbed by the slots62, 63, 64, 65, whereby distortion of the BGA package 61 caused by theshock transmitted thereto can be reduced.

[0088] Next, a sixth embodiment of the present invention will bedescribed with reference to FIG. 9.

[0089]FIG. 9 is a plan view showing the configuration of a printedcircuit board according to the sixth embodiment. The printed circuitboard 70 has slots 73, 74, 75, 76 formed in the four corners thereof atrespective locations outward of a component mounting area in which a BGApackage 71 and other components are mounted. Each of the slots 73, 74,75, 76 has a width determined according to the thickness of the printedcircuit board 70. For instance, when the printed circuit board 70 has athickness of 1.6 mm, it is preferred that the slots 73, 74, 75, 76 areeach formed to have a width of approximately 2 mm. When the printedcircuit board 70 has a thickness of 0.8 mm, it is preferred that theslots 73, 74, 75, 76 are each formed to have a width of approximately 1mm.

[0090] According to this embodiment, since the printed circuit board 70is formed with the slots 73, 74, 75, 76, even if the printed circuitboard 70 is carelessly dropped, a shock due to the drop is absorbed bythe slots 73, 74, 75, 76 in the four corners of the printed circuitboard, whereby distortion of the BGA package 71 caused by the shocktransmitted thereto can be reduced.

[0091] Although in the sixth embodiment, the slots 73, 74, 75, 76 areformed in the four corner portions of the printed circuit board, this isnot limitative, but the printed circuit board 70 may have slots 77 a, 77b, 77 c, 77 d, 77 e, 77 f, 77 g, 77 h formed along the four sidesthereof as shown in FIG. 10. This variation provides the same effect asobtained by the sixth embodiment.

[0092] Next, a seventh embodiment of the present invention will bedescribed with reference to FIGS. 11(A) and 11(B).

[0093] FIGS. 11(A) and 11(B) show the configuration of a printed circuitboard according to the seventh embodiment. FIG. 11(A) is a plan viewshowing part of the printed circuit board, while FIG. 11(B) is asectional view taken on line X5-X5 of FIG. 11(A). The printed circuitboard 80 has a thin portion 82 grooved in a manner enclosing a BGApackage area in which a BGA package 81 is mounted. As shown in FIG.11(B), the thin portion 82 is formed by grooving a front side (top) anda reverse side (bottom) of the printed circuit board 80 at oppositelocations. The thin portion 82 has a thickness which is determinedaccording to the thickness of the other part of the printed circuitboard 80. For instance, when the other part of the printed circuit board80 has a thickness of 1.6 mm, it is preferred that the thin portion 82is formed to have a thickness of approximately 0.8 mm.

[0094] It should be noted that wiring 83 extending across the thinportion 82 can be arranged in an inner layer of the printed circuitboard 80.

[0095] According to this embodiment, since the printed circuit board 80is formed with the thin portion 82, even if the printed circuit board 80is carelessly dropped, a shock due to the drop is absorbed by the thinportion 82, whereby distortion of the soldered portions of the BGApackage 81 caused by the shock transmitted thereto can be reduced.

[0096] Next, an eighth embodiment of the present invention will bedescribed with reference to FIGS. 12(A) and 12(B).

[0097] FIGS. 12(A) and 12(B) show the configuration of a printed circuitboard according to the eighth embodiment. FIG. 12(A) is a plan viewshowing part of the printed circuit board, while FIG. 12(B) is a sideview showing a fixing member in a state mounted on a BGA package and theprinted circuit board. The printed circuit board 90 of the eighthembodiment has a component mounting surface 91 onto which the BGApackage 92 is mounted. The BGA package 92 is mounted on the printedcircuit board 90 with four corners thereof fixed to the printed circuitboard by the respective fixing members 93, 94, 95, 96. FIG. 12(B) showsthe fixing member 93 in a mounted state. The fixing member 93 is a chipcomponent, such as a resistor or a capacitor, which can be automaticallymounted. The fixing member 93 is comprised of a presser portion 93 a forpressing the BGA package 92 downward and a soldered portion 93 bsoldered to the surface of the printed circuit board 90. The solderedportion 93 b is formed to have a suitable angle θ with respect to thesurface of the printed circuit board.

[0098] Similarly to the BGA package 92, the fixing member 93 is mountedon a footprint 90 a having solder paste 93 c applied thereto, by anautomatic mounting apparatus. Then, the solder paste 93 c is melted whenthe BGA package 92, the printed circuit board, and the fixing member 93are within a heating apparatus to thereby secure the fixing member 93onto the printed circuit board. During the process, the fixing member93, which has the soldered portion 93 b formed to have the suitableangle θ with respect to the surface of the printed circuit board, can beflexibly set according to the height of the BGA package 92.

[0099] The other fixing members 94, 95, 96 each have substantially thesame construction as that of the fixing member 93 described above indetail. Hence, description of the fixing members 94, 95, 96 is omitted.

[0100] According to the above embodiment, since the four corners of theBGA package 92 are secured to the printed circuit board 90 by the fixingmembers 93, 94, 95, 96, even if the printed circuit board 90 iscarelessly dropped, a shock transmitted to soldered portions of the BGApackage 92 can be reduced.

[0101] It is noted that although in the above description, the fixingmember 93 is formed by a chip component such as a resistor or acapacitor, this is not limitative, but any solderable component, such asa molded/deposited component, a metal component, and a ceramiccomponent, may be employed as a fixing member 93.

[0102] FIGS. 13(A) and 13(B) show the construction of a mountingcomponent for mounting the fixing member 93 according to the eighthembodiment or the like. FIG. 13(A) is a view schematically showing thewhole construction of the mounting component, while FIG. 13(B) is anenlarged view showing part of the same. The mounting component 97 is aroll of a tape 98 wound around a reel. The tape 98 has a plurality ofrecesses 99 formed by press molding at equally-spaced intervals. Each ofthe recesses 99 contains one electronic component, such as a fixingmember 93.

[0103] The mounting component 97 is installed in the automatic mountingapparatus, and the fixing members 93 contained in the respectiverecesses 99 are taken out one by one by a robot hand, and placed on theprinted circuit board 90.

[0104] Next, a ninth embodiment of the present invention will bedescribed with reference to FIGS. 14(A) and 14(B).

[0105] FIGS. 14(A) and 14(B) show a printed circuit board according tothe ninth embodiment. FIG. 14(A) is a plan view showing part of theprinted circuit board, while FIG. 14(B) is a side view showing a fixingmember in a state mounted on a BGA package and the printed circuitboard. The printed circuit board 100 has a component mounting surface101 on which the BGA package 102 is mounted. The BGA package 102 issecured to the component mounting surface 101 in a state presseddownward by a fixing member 103. The fixing member 103 is comprised of aframe portion 103 a for retaining the BGA package 102 at the edgesthereof, a presser portion 103 b for pressing the central portion of theBGA package 102 downward, and terminal portions 103 c, 103 d, 103 e, 103f formed at the four corners. The fixing member 103 is formed in onepiece by a solderable member, such as a molded/deposited member, a metalmember, or a ceramic member.

[0106]FIG. 14(B) shows the terminal portion 103 c in a mounted state.The terminal portion 103 c has an end thereof formed as a solderedportion 104 c formed to have a suitable angle θ1 with respect to thesurface of the printed circuit board 100.

[0107] The fixing member 103 constructed as above is carried in a trayand automatically mounted by a mounting apparatus for use in mountingdeformed members. More specifically, similarly to the BGA package 102,the fixing member 103 is placed on a footprint 100 a having solder paste105 applied thereto, by the automatic mounting apparatus, and then thesolder paste 105 is melted when the BGA package 102, the printed circuitboard and the fixing member are within a heating apparatus to therebysecure the fixing member 103 onto the printed circuit board. During themounting process, the fixing member 103, which has the soldered portion104 c formed to have the suitable angle θ1 with respect to the surfaceof the printed circuit board can be flexibly set according to the heightof the BGA package 102.

[0108] The other terminal portions 103 d, 103 e, 103 f each havesubstantially the same construction as that of the terminal portion 103c described above in detail. Hence, description of the terminal portions103 d, 103 e, 103 f is omitted.

[0109] According to the above embodiment, since the BGA package 102 issecured to the printed circuit board 100 by the fixing members 103constructed as above, even if the printed circuit board 100 iscarelessly dropped, a shock transmitted to soldered portions of the BGApackage 100 can be reduced.

[0110] Next, a tenth embodiment of the present invention will bedescribed with reference to FIGS. 15 and 16.

[0111]FIG. 15 is a bottom view showing the configuration of a mountingsurface of a BGA package according to the tenth embodiment. The mountingsurface 111 of the BGA package 110 is formed with a large number ofreinforcing solder bumps 112 at equally-spaced intervals alongperipheral portions thereof enclosing a solder bump area 11 a for solderbumps for circuit connection. The reinforcing solder bumps 112 areformed on respective footprints, not shown in FIG. 15, such that theyare connected in pairs by connecting patterns 113.

[0112]FIG. 16 is a plan view showing the configuration of a printedcircuit board according to the tenth embodiment. The printed circuitboard 120 has an area 120 a in which the BGA package 110 is mounted, andfootprints 121 to which the respective reinforcing solder bumps 112 onthe BGA package 110 are connected are formed at locations correspondingto the reinforcing solder bumps. Further, out of the footprints 121, onediagonally opposite pair of footprints 121 a, 121 b are connected torespective through holes 123, 124 formed through the printed circuitboard 120, while the other diagonally opposite pair of footprints 121 c,121 d are connected to respective through holes 126, 127.

[0113] In order to inspect the printed circuit board 120 having the BGApackage 110 mounted thereon, a so-called bridge circuit is formed byconnecting a power supply 125 between the through holes 123, 124, and atthe same time connecting a galvanometer 128 between the through holes126, 127.

[0114] When the BGA package 110 has no defective soldered portions, thevalue of the galvanometer 128 indicates an equilibrium value. On theother hand, when a shock due to a drop of the printed circuit board 120have caused a breakaway or a crack of the footprints or the connectingpatterns 113 for the reinforcing solder bumps 112 on the BGA package110, or the footprints 121 or a pattern 122 on the printed circuit board120, the defective portion undergoes a change in the resistance value,which causes a change in the value of the galvanometer 128. From this,it is possible to detect a defect which cannot be visually detected.

[0115] Next, an eleventh embodiment will be described with reference toFIGS. 17(A) and 17(B).

[0116] FIGS. 17(A) and 17(B) show the configuration of a printed circuitboard according to the eleventh embodiment. FIG. 17(A) is a plan viewshowing part of the printed circuit board, while FIG. 17(B) is a viewtaken on line X6-X6 of FIG. 17(A). A BGA package area of the printedcircuit board 130 in which a BGA package is mounted is formed withfootprints 131 to which are connected solder bumps for circuitconnection. The footprints 131 are formed at locations opposed to therespective solder bumps. The top of the printed circuit board 130 exceptthe portions at which the footprints 131 are formed is covered with aresist 132.

[0117] Further, out of the footprints 131, footprints 131 a, 131 b, 131c, 131 d, 131 e arranged in an outer corner portion of the printedcircuit board 130 are each formed to have a larger size than the otherfootprints 131. However, each of the footprints 131 a, 131 b, 131 c, 131d, 131 e has only a portion thereof exposed for connection with thecorresponding solder bump on the BGA package, and the other portionthereof covered with a portion 132 a of the resist 132.

[0118] This configuration makes it possible to increase joint strengthbetween the corner footprints 131 a, 131 b, 131 c, 131 d, 131 e, whichare sensitive to a shock from outside, and the printed circuit board130, thereby preventing the footprints 131 a, 131 b, 131 c, 131 d, 131 efrom breaking away from the printed circuit board 130 when a shock isapplied to the printed circuit board 130 e.g. due to a drop of the same.

[0119] Further, it is preferred that the BGA package mounted on theprinted circuit board 130 is formed with footprints for solder bumpsthereof, which are configured similarly to the above footprints of theprinted circuit board 130.

[0120] As described above, according to the present invention, an areaon a BGA package located outward of a circuit-connecting solder bumparea is formed with reinforcing solder bumps which can be connected to areinforcing pattern(s) formed on a printed circuit board, so that oncethe reinforcing solder bumps are connected to the reinforcing pattern(s)e.g. by soldering, even if a shock is applied to the package e.g. whenthe printed circuit board having the package mounted thereon iscarelessly dropped, the shock applied to the outer or peripheral portionof the package, which is most sensitive to such a shock, is absorbed bythe reinforcing solder bumps and the reinforcing pattern(s) which haveno electrical connection with the circuits. Therefore, the inventionmakes it possible to prevent a breakaway or a crack of the footprintsand the like formed at the circuit-connecting portions of the electroniccomponent package.

[0121] Moreover, since extra materials such as an adhesive can bedispensed with, it is possible to reduce the number of manufacturingsteps. Further, even if the electronic component package becomesdefective, it is not required to discard the printed circuit boardtogether with the package. This helps to prevent waste of materials aswell as an increase in manufacturing costs.

[0122] Furthermore, the present invention provides the method ofchecking a printed circuit board having an electronic component packageof ball grid array type mounted thereon, in which a bridge circuit isformed between the reinforcing solder bumps formed on the electroniccomponent package and the reinforcing footprints formed on the printedcircuit board, and then by detecting a change in the resistance value ofthe bridge circuit, a defective state of the printed circuit board isdetected. This makes it possible to detect a defect which cannot bevisually detected.

[0123] The foregoing is considered as illustrative only of theprinciples of the present invention. Further, since numerousmodifications and changes will readily occur to those skilled in theart, it is not desired to limit the invention to the exact constructionand applications shown and described, and accordingly, all suitablemodifications and equivalents may be regarded as falling within thescope of the invention in the appended claims and their equivalents.

What is claimed is:
 1. An electronic component package of ball gridarray type, comprising: a plurality of circuit-connecting bumps formedin a predetermined area, and at least one reinforcing bump formed in anarea located outward of said predetermined area, in a manner such thatsaid at least one reinforcing bump is connectable to at least onereinforcing pattern formed on a printed circuit board.
 2. An electroniccomponent package according to claim 1, wherein a plurality of saidreinforcing bump are formed on a single pattern.
 3. An electroniccomponent package according to claim 1, wherein said at least onereinforcing bump is formed in at least one corner of said electroniccomponent package.
 4. An electronic component package according to claim1, wherein said at least one reinforcing bump is formed along at leastone side of said electronic component package.
 5. An electroniccomponent package according to claim 1, including a body having acorner, an area for said at least one reinforcing bump is formed in amanner of projecting from an end face of said corner.
 6. An electroniccomponent package of ball grid array type, comprising: a plurality offootprints; and a plurality of circuit-connecting bumps formed on saidfootprints, respectively, said footprints being formed in a manner suchthat at least ones of said footprints arranged in corners of saidelectronic component package are larger in size than others of saidfootprints.
 7. A printed circuit board for being mounted with anelectronic component package of ball grid array type, comprising: atleast one reinforcing pattern formed in an area located outward of anarea to which circuit-connecting bumps formed on said electroniccomponent package are soldered, said at least one reinforcing patternbeing formed in a manner such that said at least one reinforcing patternis connectable to at least one reinforcing bump formed on saidelectronic component package.
 8. A printed circuit board according toclaim 7, wherein said at least one reinforcing bump is formed in amanner such that said at least one reinforcing pattern is connectable toa plurality of said reinforcing bumps.
 9. A printed circuit boardaccording to claim 7, wherein said at least one reinforcing bump isformed in a corner of said electronic component package, and whereinsaid at least one reinforcing pattern is formed at a location opposed tosaid at least one reinforcing bump formed in said corner of saidelectronic component package.
 10. A printed circuit board according toclaim 7, wherein said at least one reinforcing bump is formed along aside of said electronic component package, and wherein said at least onereinforcing pattern is formed at a location opposed to said at least onereinforcing bump formed along said side of said electronic componentpackage.
 11. A printed circuit board for being mounted with anelectronic component package of ball grid array type, comprising: atleast one slotted portion formed in an area located outward of anelectronic component package area on which said electronic componentpackage is mounted.
 12. A printed circuit board for being mounted withan electronic component package of ball grid array type, comprising: atleast one thin portion formed in an area located outward of anelectronic component package area on which said electronic componentpackage is mounted.
 13. A printed circuit board mounted with anelectronic component package of ball grid array type, said electroniccomponent package including circuit-connecting bumps formed in apredetermined area, and reinforcing bumps formed in an area outward ofsaid predetermined area, said printed circuit board comprising: amounting surface for mounting said electronic component package thereon;a reinforcing pattern formed on said mounting surface in a manner ofcorresponding to said reinforcing bumps, said reinforcing bumps beingconnected to said reinforcing pattern.
 14. A printed circuit boardmounted with an electronic component package of ball grid array type,comprising: a mounting surface on which said electronic componentpackage having an end is mounted; a pattern formed on said mountingsurface; and a fixing member for retaining said end of said electroniccomponent package to thereby secure said electronic component packageonto said mounting surface, said fixing member comprising: a presserportion for pressing a top surface of said electronic component package,and an attachment portion for being attached to said pattern on saidmounting surface.
 15. A printed circuit board according to claim 14,wherein said attachment portion of said fixing member is inclined withrespect to the surface of said printed circuit boad.
 16. A printedcircuit board mounted with an electronic component package of ball gridarray type, said electronic component package includingcircuit-connecting bumps formed thereon, said printed circuit boardcomprising: a plurality of footprints connected to saidcircuit-connecting bumps, respectively, said footprints being formed ina manner such that at least ones of said footprints arranged in cornersof said printed circuit board are larger in size than others of saidfootprints.
 17. A method of inspecting a printed circuit board having anelectronic component package mounted thereon, comprising the steps of:forming a bridge circuit between reinforcing bumps formed on saidelectronic component package, and reinforcing footprints formed on saidprinted circuit board in a manner such that said reinforcing bumps areconnected to said reinforcing footprints; and detecting a change in aresistance value of said bridge circuit to thereby detect a defect ofsaid printed circuit board.